One known type of contactless torque sensor is a magnetostrictive torque sensor for detecting torque based on a change in magnetic properties due to magnetostriction. Such a magnetostrictive torque sensor is used to detect the steering torque of an automotive steering apparatus (see Japanese Laid-Open Patent Publication No. 2004-309184).
The magnetostrictive torque sensor of the type described above comprises two magnetostrictive films (a first magnetostrictive film and a second magnetostrictive film) mounted on a shaft and having different magnetic anisotropic properties, and a first shaft and a second shaft, which are disposed in confronting relation to the first magnetostrictive film and the second magnetostrictive film, respectively. When a torque (twist) is applied to the shaft to thereby twist the shaft, magnetic permeabilities of the first and second magnetostrictive films change, thereby changing inductances in the first and second detecting coils. Therefore, the torque can be detected as changes in impedance or induced voltages of the first and second detecting coils.